Like this:

John German has barely had time to catch his breath all week between appearances on TV news channel and radio phone-in shows. He’s … a grey-haired automotive engineer…
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German earns a modest salary as US co-lead of the International Council on Clean Transportation (ICCT) a small nonprofit organisation dedicated to helping to reduce vehicle emissions and has an annual budget of just $12m.
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German explained that the idea to carry out the test, which he described as “very ordinary”, came from Peter Mock, a colleague in Europe, who noticed discrepancies in the emissions of the diesel VW Passat and VW Jetta.
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Then German sourced a Passat, Jetta and a BMW X5 (which also showed emissions discrepancies in Europe) and “had a drive around”. “The VWs were massively exceeding their official emissions readings in normal driving conditions…”
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Arvind Thiruvengadam, a research assistant professor at WVU, who conducted the tests said: “We were doubting ourselves and our procedures and making sure to double check that we were not doing anything wrong.
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German published the research in May 2014 and handed it over to the Environment Protection Agency (EPA). …“We did send a courtesy copy to VW…”
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There was no response from the EPA either, but keen-eyed German noticed an EPA press release in which VW agreed to recall almost 500,000 vehicles in December 2014 to reinstall software, which it said would solve the higher-than-expected emissions.
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German said it was unclear how the defeat device software worked, but the software could work by detecting periods when the steering column wasn’t turning but the wheels were which would indicate the car was on dynamo-meters for testing, or could also test for the precise uniform temperature that the tests are carried out at.